Continuous hydrostatic extrusion die assembly and method for using it in forming extruded parts

ABSTRACT

An extrusion die assembly and method for extruding circular billets with a relatively high length-to-diameter ratio comprising an extruding die located in one end of a sealed container which is adapted to receive a hydraulic ram, the ram being actuated by a hydraulic press, means for positioning and locating a billet in proper registry with respect to the die, means for introducing fluid into the chamber around the billet as the ram is withdrawn, the billet being extruded hydrostatically through the die as the ram is subsequently advanced in the fluid chamber, the billet forcing the end of the preceding billet through the die as it is advanced toward the entrance region of the die whereby a continuous extrusion of successive billets may be achieved as each billet is subjected to hydrostatic loading, the contiguous relationship of the billets preventing hydrostatic shock due to expulsion of a billet from the die and sudden decompression of the fluid.

United States Patent Hauser et a1.

[ June 18, 1974 [75] Inventors: Gotz S. Hauser, Southfield; Robert B. Melmoth, Farmington, both of Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[22] Filed: May 25, 1972 [21] Appl. No.: 256,882

[52] US Cl. 72/60, 72/27] [51] Int. Cl. B216 23/08 [58] Field of Search 72/60, 264, 270, 271

[56] References Cited UNITED STATES PATENTS 2,879,887 3/1959 Hawtin 72/264 3,126,096 3/1964 Gerard et al 72/60 3,380,270 4/1968 Sauve l 72/60 3,382,691 5/1968 Green l 72/60 3,434,320 3/1969 Green 72/60 3,451,240 6/1969 Sauve 72/60 3,531,965 10/1970 Nilsson l 72/60 3,677,049 7/1972 Cartwright et. a1 72/60 3,677,050 7/1972 Ahmed 72/60 Primary ExaminerRichard J. Herbst Attorney, Agent, or Firm-Donald J. Harrington; Keith L. Zerschling 5 7 ABSTRACT An extrusion die assembly and method for extruding circular billets with a relatively high length-todiameter ratio comprising an extruding die located in one end of a sealed container which is adapted to receive a hydraulic ram, the ram being actuated by a hydraulic press, means for positioning and locating a billet in proper registry with respect to the die, means for introducing fluid into the chamber around the billet as the ram is withdrawn, the billet being extruded hydrostatically through the die as the ram is subsequently advanced in the fluid chamber, the billet forcing the end of the preceding billet through the die as it is advanced toward the entrance region of the die whereby a continuous extrusion of successive billets may be achieved as each billet is subjected to hydrostatic loading, the contiguous relationship of the billets preventing hydrostatic shock due to expulsion of a billet from the die and sudden decompression of the fluid.

2 Claims, 5 Drawing Figures PATENTEDJuu 18 m4 sham a or 2 CONTINUOUS HYDROSTATIC EXTRUSION DIE ASSEMBLY AND METHOD FOR USING IT IN FORMING EXTRUDED PARTS GENERAL DESCRIPTION OF THE INVENTION Our invention comprises an improvement in hydrostatic extrusion methods and extrusion dies. In conventional hydrostatic extrusion of parts having high length to diameter ratios such as bars and tubing, it is customary practice to locate an extrusion die at one side of a hydrostatic pressure chamber. The die is mounted in the path of movement of a circular billet. The billet and the die are manipulated into proper position by appropriate fixtures which can be retracted after the extrusion operation begins. A hydrostatic pressure chamber formed in a reinforced container is advanced toward the billet so that one end of the billet is received within one end of the pressure chamber. The container is moved by a hydraulic press. The movable piston of the press carries a ram that centers the other end of the pressure chamber. The ram and the billet are separated by a movable sealing piston. As fluid is pumped into the hydraulic press, the ram increases the hydrostatic pressure of the fluid which is pumped into the hydrostatic pressure chamber around the billet. Asthe container is advanced toward the die, the adjacent end of the hydrostatic chamber becomes sealed. The opposite end of the hydrostatic chamber is sealed by the hydraulic ram and movable piston.

As the ram advances, the billet is extruded hydrostatically through the die. A portion of the billet, which is called the butt portion, is not extruded through the die because this would produce undesirable shock forces upon decompression of the fluid. Instead the container is retracted by the hydraulic press and the butt is cut from the extruded part. The fluid that is used for the hydrostatic extrusion is lost as the container is withdrawn. Following these steps itis necessary to reinsert a second billet and to reposition the extruding die as the foregoing operation is repeated. Only one extruded part may be obtained for each extrusion cycle. n It is an object of our invention to reduce the operating cycle time to obtain extruded parts. This is done by performing the extrusion operation continuously with a series of billets acting in end-to-end registering relationship as they are advanced toward the extrusion die. As each billet is extruded hydrostatically, it forces the preceding billet through the extrusion die thereby eliminating the need for cutting off the end of the preceding billet and interrupting the operating cycle as a fresh billet is introduced into the container.

In our improved extrusion cycle a new billet is introduced by placing it behind the butt of a preceding billet as the ram is withdrawn. The two billets then are extruded together in series relationshipOnly a small portion of the fluid flows out of the die during each cycle. The forward end of one billet is piloted in the extrusion die as the preceding billet is advanced through the die. The forward end of the advancing billet seals the high pressure cavity, but the fluid in the cavity will not be expelled through the die as the preceding billet is discharged.

The high pressure fluid in the pressure chamber is allowed to surround the die portion of the assembly thereby resisting the tendency of the die to deform radially.

The pressure acting on the die, unlike the directacting mechanical forces of conventional extrusion mechanisms, creates hydrostatic forces on the die. The pressure is created by the hydraulic plunger received slidably in the working chamber of the die container. Each time the plunger is withdrawn, upon retraction of the ram, a new billet may be inserted.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. 1 shows a series of steps for a conventional extrusion die mechanism. Each step is identified by a separate letter A through H.

FIG. 2 shows in cross-section an extrusion die and die container embodying the improvements of our invention.

FIG. 3 is an end view of the die used in the assembly of FIG. 2 as seen from the plane of section line 33 of FIG. 2.

FIG. 4 is an enlarged view of a corner of a billet after it is advanced into the extrusion die.

FIG. 5 is a view similarto FIG. 2 although it shows the billet in a position near the entrance of the extrusion die.

PARTICULAR DESCRIPTION OF THE INVENTION The prior art apparatus of FIG. 1 includes a hydraulic ram 10 and an extrusion die 12. Ram 10 includes a ram cylinder 14 and a ram piston 16. A plunger 18 is carried by piston 16 and is received within a billet container 20. This may comprise a series of cylindrical steel sleeves, the innermost of which slidably receives plunger 18. A pressure cavity 22 in the innermost steel sleeve is situated between the end of the plunger 18 and a sealing piston 24.

The die- 12 is advanced toward the support 26 and a billet 28 is positioned by a suitable transfer mechanism and mounting fixture in alignment with the die. This is indicated in diagram B. The billet container is advanced toward the die so that the billet 28 is received within the innermost sleeve of the container until it engages the end of the sealing piston 24. The positioning fixtures for the die and the billet then are withdrawn as indicated in view C of FIG.'1. As indicated in view D the ram piston 14 is advanced by pumping fluid into the ram cylinder. The pressure medium passes through a spring-loaded valve in the sealing piston and surrounds the billet as the right-hand end of the billet container seals against the packing seal 30 located directly against the support 26. In view E the plunger 18 is shown after it has advanced beyond the port 32 through which fluid is pumped into the container. The plunger seals off the fluid supply to the container and as the piston 16 is advanced, the pressure in the chamber 22 increases thereby extruding the billet through the die. The ram is stopped before the die is fully extruded, as indicated in view F. The ram then is retracted and carries the billet container with it as indicated in view G. The die and the butt end of the billet remain in the position shown in view G where they may be cut off by a suitable friction cutting wheel 34. The butt end of the billet and the die then are removed, as shown in view H, and a new billet is simultaneously fed into the container so that the cycle can be repeated.

It is necessary to employ the cutting off step since it is not possible with such a conventional extrusion assembly to extrude fully the billet through the die as this would create an undesirable shock loading due to the sudden decompression of the working fluid in the billet container.

The improvement of our invention differs from the conventional system by its continuous extrusion characteristic. It is capable of extruding a series of billets, one following the other, without the necessity for the cutting operation and without the hydrostatic shock loads due to sudden compression of the extruding fluid. The extrusion die assembly of our invention includes a billet container 40 having a center pressure chamber 42. A hydraulic ram 44 is received within one end of the container and is sealed by a suitable peripheral seal 46. The end of the ram 44 carries a cap 48 which is adapted to engage the adjacent end of a billet 50 when the latter is loaded into the chamber 42. Fluid may be admitted to the chamber 42 through a suitable supply port 52. A one-way flow valve prevents reversal of fluid flow through the port 52.

An extrusion die 62 is received in the outlet end of the chamber 42. It is formed with an irregular periphery as shown in FIG. 3, so that spaces are formed between the inner wall of the chamber 42 and the periphery of the die 62. Fluid pressure within the chamber 42 then surrounds the die 62 causing a radially inward force acting on the die which opposes the tendancy of the die to deform in a radially outward direction as a result of the extrusion forces. The recesses are identified by reference character 64.

The upper end of the die has formed thereon a circular cap 66 which has a tapered central opening. The degree of taper may be about 7 or less. The end of the billet 50 is received within the tapered opening of cap 66 and is piloted toward the extrusion die opening as the plunger 44 is advanced by the hydraulic ram not shown.

The cap 48 has a peripheral taper for appropriately piloting the adjacent end of the billet 50. The upper end of the die 62 is slotted as shown in FIG. 4 at 70 to permit exit of fluid that is trapped between the trailing end of one billet and the leading end of the succeeding billet as the succeeding billet is advanced into the die. The slots 70 communicate with axially directed passages 72 in the die which lead to the exterior of the assembly.

In FIG. 5 we have shown the billet just prior to the extrusion operation. FIG. 2 shows the billet after it has been advanced through the extrusion die upon advancing movement of the ram. The extrusion forces acting on the billet are hydrostatic forces rather than mechanical forces since the fluid displaced by the ram results in movement of the billet at a rate that is greater than the rate of advancement of the ram. As the succeeding billet descends the liquid that is trapped between that billet and the preceding billet escapes so that the pressure of the fluid at that time remains atmospheric. The lower end of the billet creates a seal between the upper and lower cavities. As the ram is withdrawn a short distance makeup fluid is added through the port 52. When the ram again is advanced toward the die it begins the extrusion operation in a purely hydrostatic manner. The cap 48 makes no contact with the billet. The pressure above the billet and around the die rises until the extrusion of the billet begins. When the lower part of the billet passes the slots in the die, the butt of the preceding billet also is extruded. When the butt leaves the die, there is little shock because the billet being extruded behind it acts as a force stabilizer. The extrusion of the billet is terminated when the upper surface of the butt portion of the billet passes beyond the die slots.

The need for providing a piston seal or for providing a seal between the billet and the surrounding billet chamber wall is not required in our assembly. This simplifies the overall extrusion assembly. Also the number of extrusion steps is reduced in number in comparison to prior art methods because of the continuous feeding and extrusion action that occurs as one billet is advanced simultaneously with the expulsion of the preceding billet through the die.

Having described a preferred form of our invention, what we claim and desire to secure by U.S. Letters Patent is:

l. A hydrostatic extrusion apparatus comprising a billet container having a central opening formed therein, an extrusion die in one end of said opening, a plunger adapted to be received within the other end of said opening, a ram for actuating said plunger toward said extrusion die, said opening being adapted to receive therein a billet, a sealing cap portion at the inward end of said extrusion die, said cap portion having a central opening adapted to receive one end of said billet thereby creating a fluid seal, means for introducing working fluid around said billet within said opening whereby hydrostatic extrusion forces are created on said billet as said plunger is advanced into said opening, said die having located therein the trailing end of a billet from a preceding extrusion operation as said one end of said first named billet is received within said cap portion whereby said preceding billet is extruded through said die in advance of said first named billet as said plunger is advanced, said ram carries thereon a piloting cap adapted to engage one end of said first billet, said piloting cap having tapered portions thereon for centering said billet within said chamber as the billet is advanced toward said die to create a seal between said first billet and said die, said seal isolating the pressure in said chamber as the pressure in said chamber is increased upon advancement of said ram thereby creating a net uni-directional hydrostatic force on said first billet.

2. A hydrostatic extrusion apparatus comprising a billet container having a central opening formed therein, an extrusion die in one end of said opening, a plunger adapted to be received within the other end of said opening, a ram for actuating said plunger toward said extrusion die, said opening being adapted to receive therein a billet, a sealing cap portion at the inward end of said extrusion die, said cap portion having a central opening adapted to receive one end of said billet thereby creating a fluid seal, means for introducing working fluid around said billet within said opening whereby hydrostatic extrusion forces are created on said billet as said plunger is advanced into said opening, said die having located therein the trailing end of a billet from a preceding extrusion operation as said one end of said first named billet is received within said cap portion whereby said preceding billet is extruded through said die in advance of said first named billet as said plunger is advanced, the advancing end of said first named billet and the trailing end of said preceding billet define therebetween a pressure chamber, the sealing action of said first named billet with respect to said die isolating the working fluid in said chamber from said and said die, said seal isolating the pressure in said chamber as the pressure in said chamber is increased upon advancement of said ram thereby creating a net uni-directional hydrostatic force on said first billet. 

1. A hydrostatic extrusion apparatus comprising a billet container having a central opening formed therein, an extrusion die in one end of said opening, a plunger adapted to be received within the other end of said opening, a ram for actuating said plunger toward said extrusion die, said opening being adapted to receive therein a billet, a sealing cap portion at the inward end of said extrusion die, said cap portion having a central opening adapted to receive one end of said billet thereby creating a fluid seal, means for introducing working fluid around said billet within said opening whereby hydrostatic extrusion forces are created on said billet as said plunger is advanced into said opening, said die having located therein the trailing end of a billet from a preceding extrusion operation as said one end of said first named billet is received within said cap portion whereby said preceding billet is extruded through said die in advance of said first named billet as said plunger is advanced, said ram carries thereon a piloting cap adapted to engage one end of said first billet, said piloting cap having tapered portions thereon for centering said billet within said chamber as the billet is advanced toward said die to create a seal between said first billet and said die, said seal isolating the pressure in said chamber as the pressure in said chamber is increased upon advancement of said ram thereby creating a net uni-directional hydrostatic force on said first billet.
 2. A hydrostatic extrusion apparatus comprising a billet container having a central opening formed therein, an extrusion die in one end of said opening, a plunger adapted to be received within the other end of said opening, a ram for actuating said plunger toward said extrusion die, said opening being adapted to receive therein a billet, a sealing cap portion at the inward end of said extrusion die, said cap portion having a central opening adapted to receive one end of said billet thereby creating a fluid seal, means for introducing working fluid around said billet within said opening whereby hydrostatic extrusion forces are created on said billet as said plunger is advanced into said opening, said die having located therein the trailing end of a billet from a preceding extrusion operation as said one end of said first named billet is received within said cap portion whereby said preceding billet is extruded through said die in advance of said first named billet as said plunger is advanced, the advancing end of said first named billet and the trailing end of said preceding billet define therebetween a pressure chamber, the sealing action of said first named billet with respect to said die isolating the working fluid in said chamber from said opening, said ram carries thereon a piloting cap adapted to engage one end of said first billet, said piloting cap having tapered portions thereon for centering said billet within said chamber as the billet is advanced toward said die to create a seal between said first billet and said die, said seal isolating the pressure in said chamber as the pressure in said chamber is increased upon advancement of said ram thereby creating a net uni-directional hydrostatic force on said first billet. 